Audi wants to be world's leading luxury nameplate by 2015, which is no small task. Volkswagen Group's mainstream upscale division has been on a roll lately, and has now worked its way to near 900,000 global sales per year. Trouble is, the kings of the premium hill--BMW, Lexus, and Mercedes-Benz--each draw some 1.4 million annual sales. That's a big gap to close over seven years, especially since Audi's foes aren't known for making mistakes. That's why Audi R8is racing to redesign existing models while entering market sectors where it has never competed before, and may the best brand win.Prime among the first-time offerings--and a symbol of Audi's drive to the top--is the new-for-2008 R8 coupe, a two-seat mid-engine cruise missile based on the wedgy-edgy Gallardo by Lamborghini, the legendary Italian marque that Audi took over about a decade ago. Widely hailed for its striking looks, top-notch engineering and sizzling performance, the V8-powered all-wheel-drive R8 became a fast first-year sellout. But Audi knows the car can't rest on these laurels for long. After all, the "exoticar" market is notoriously fickle, and nothing hurts an automaker's image more than a performance flagship that's soon left in the dust. No surprise, then, that sources expect the 2010 Audi R8 to offer more power and an open-air option too